His point is a good one: that interplanetary travel is extremely expensive in terms of resources and that it’s quite unlikely that an extraterrestrial civilization would go to all the trouble just to say hi. On the other hand though, interplanetary travel is SO expensive that I can’t imagine Earth would have anything worth making the journey for that couldn’t be accomplished more cheaply with terraforming or mining other, closer planets.

Also, there’s still the ever-so-slight possibility that there is a way to cross vast distances without a massive energy cost, maybe even at faster-than-light speeds (shut up, there might be!), and that alien civilizations have mastered it. That would seem to knock his argument asunder.

It’s true we still have a lot to learn about our own planet but you could have said the same thing about Africa around 100,000 years ago when our species started wandering northward. You can’t contain human curiosity, a fact Dr. Hawking probably knows better than anyone.

I do admit that he has some point, an alien civilization that can travel from star to star for whatever reason has certainly got a few technological toys we certainly cannot think up, and thus we would be certainly ants in comparison. In fact I think the only real positive alien contact we could perhaps get is if we had a long delay conversation between us screaming into the void of space and them doing the same in reply to us. Hopefully with the both of our civilizations at equivalent technological levels with them having figured out a few tricks we haven’t yet and the same for ourselves so we can make some equal trades. This does all presuppose the fact other intelligent alien life is out there, which optimistically is something I do hope to be true.

The problem with communicating anything of substance between us and an alien civiliization, is that it’s is enormously difficult. We don’t have a common basis to start from. Oh yes, we live in the same universe, but our symbols are completely different. We’re talking about a difficulty that that made Annie Sullivan’s work look like a walk in the park. Training your cat is easier.

You remember the Arecibo Message? The senders gave that message to several astronomers and mathemeticians. No one — let me repeat that — NO ONE decoded that message. It was just too complicated. I’m not even sure if anyone would have noticed it as being artificial.

Given the problems of understanding each other, and a latency measured in lifetimes, I doubt there’s anything either of us could say beyond “Hey!” We’d be dogs barking in the night.

if they are capable of traveling to distant stars, i guess these aliens would also have the technology to notice us with or without us trying to establish communication.
does anyone know if i can watch the show online? (my location: germany)

What resources? Water? There’s water in the Oort Cloud and it’ll be much easier to grab it there than pulling it off of Earth. Minerals? It would be easier to grab it from asteroids in zero gravity. I’m curious what we would have that would be worth coming all the way here for. Unless we just taste good.

Tend to agree with Zadaz. If we have anything interesting to contribute, it’s simply the fact that someone else is out there and possibly an alternative way of viewing the universe. (And the nice thing about culture is that you can trade it without losing it, if you’re careful.)

As others have pointed out, we’re demonstrating that the chances of contact are vanishingly small unless a VERY deliberate and VERY sustained effort is made. As technology advances, the easy-to-recognize-as-intelligent transmissions get replaced by compressed and spread-spectrum signals which are extremely difficult to distinguish from white noise.

I disagree on your point that we wouldn’t make good slaves. After all, other humans made perfectly good slaves for thousands of years, even though they lacked the technology for advanced ship building. It would be to the alien’s advantage, rather, that we weren’t advanced because then we wouldn’t know how to revolt against their technology efficiently.

Yes I agree and so does Duncan Lunan from the The Association in Scotland for Technology and Research in Astronautics who analysed this issue in detail (Man and the Stars, 1974) and came to similar conclusions.

We are unlikely to be served (boiled or fried) and Dr Hawking really should have done some research before engaging his speech system on this subject.

But I don’t think they’ll be stripping the earth for resources just because we tried to contact them. There’s much more resources on Jupiter and Saturn. Besides, if they’re looking for planets to strip mine, it doesn’t matter if SETI tries to contact them or not. We could keep quiet and they still will come.

What we really need is some massive stealth tech that will hide the entire solar system.

It’s too late for that really; there’s already a front of our various communications travelling out from the earth, and we can’t stop that retroactively. Of course, it’d work if the aliens blinked for a few thousand years.

Check out a novel called “Signal to Noise” which raise a fascinating possibility. Interstellar travel turns out to be relatively cheap with the right scientific knowledge, but finding other intelligent life is still a very difficult problem – equivalent to winning the lottery a thousand times in a row in terms of the sheer numbers involved.

In such a scenario, the protagonist happens to bump into an alien civilization that is trying very, very hard to contact other civilizations. They can communicate instantly (with magic quantums or whatever, I can’t remember), and the human trades bits of information for amazing technological breakthroughs… until he eventually trades away the location of the earth, with disastrous consequences.

Jeez, his idea of interplanetary nomads looking for resources sounds exactly like “Independence Day.” He may have a point– any race willing to invest that much time and energy to come here would probably be mainly interested in staying. But, how do we know they 1.) breathe oxygen, 2.) are used to a similar gravitational pull– Earth could be uninhabitable to them.

Like Columbus (or Cortez) and the new world, the real threat would be microbes.

So why is space travel expensive? Do the aliens even have the same concept of expense? Maybe they have ships fueled by dark matter or something so abundant it has no cost. Maybe they have no unions and workers building the ships are super cheap. They might have nanotech ships that build themselves. Or other sufficiently advanced technology that to us is indistinguishable from magick.

Time alone is a huge expense when it comes to space travel. If these aliens lived on a planet orbiting Proxima Centauri — I don’t think it has any — and they were capable of travelling at the speed of light it’d still take them a few bits over four years to get here.

I’m fairly certain our combined chances of winning the lottery are greater than the likelyhood of there being sentient life — let alone life that advanced — so close to home.

There is still a prohibitive amount of resources required for this sort of endeavour. With what we know about the universe there just won’t be a possibility to joy-ride across the galaxy. The development of this technology that’s sufficiently advanced like you suggested would take up so much time and effort that I can’t imagine it being taken lightly even if the running costs at the end are small.

The thing is even if travel isn’t expensive in any of those ways; it’s still going to be hugely expensive in terms of time. We don’t know of any way to go faster than the speed of light. Getting around beyond your own backyard in space takes years, very likely hundreds if not thousands of years, that’s the greatest expense.

And if they’re to the point that they don’t care about the resources needed for the technology, the time it takes to travel, etc etc. If these aliens are that advanced — then why… would they want to come visit earth? I honestly think there’s a threshold where if they’re that advanced I can’t imagine them having anymore interest in us than we generally show interest in the bacterial life on the surface of a tennis ball the family Labrador plays with.

Wormhole theory exists today in our young science, and if an alien race have 100’000 year head start on their science then time and distance would probably be no problem to them. Wormholes, teleportation… Hawking is in sci-fi territory here, hence my homage to Arthur C Clarke about magick.

I don’t think aliens would come here to raid us for our resources. I think they would come here to eliminate any competition. While there might be a complex interstellar community of many different types of lifeforms living together (Star Trek and Star Wars), I think it is also a reasonable possibility that there is a genocidal race that kills off intelligent lifeforms before they can develop enough technology to pose a threat.

Given the latest findings concerning the capabilities of survival of some of our own, smaller, domestic organisms, my first and foremost cencern is whether we have already inadvertendly contaminated both the Moon and Mars with lifeforms which are alien to them.

But then I’m kinda programmed to regard the humans as the bad guys by now.

The fact that space travel is so very expensive is precisely why raiding our planet for its resources is so unlikely. It’s hard to see how it could ever be worth the energetic and material costs to travel interstellar distances.

If you want to consider high-risk extra-stellar threats, assuming hostile aliens really exist, in my opinion, they are more likely to be:

Relatively near-by supernovas – a real threat which could have caused some mass extinctions on Earth,

Medium-distance gamma-ray bursters (less common but much more powerful),

Destructive Von Neumann probes (see Greg Bear’s Forge of God), or

Relativistic bombardment aspre-emptive attack from an alien civilization that is afraid we’d do the same thing to them if we saw them first.

Stephen Hawking: “If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didnâ€™t turn out very well for the Native Americans.â€

Given that Hawking is one of the smartest people of the planet, I tend to listen to what he has to say. The Indigenous peoples of the Americas lost 80% of their population due to colonization by Europeans. It has taken 500 years for them to regain the numbers they had before Columbus got lost on his way to India. And the vast majority still live in relative poverty compared to the descendants of the colonizers. Not a pleasant scenario.

Obviously they might need to make way for an intesteller Hyperspace Byway!!! I’m surprised SH didn’t bring up examples like large vs small ant colonies, or grey squirrels vs smaller, less aggressive squirrels, etc. It is not just human history, but throughout the animal kingdom, the bigger, advanced organizations tend to wipe out less sophisticated, smaller ones. Nature red in tooth and claw. Thank God they shut down SETI!

The trouble is, other beings would face the same dilemma over whether to contact us. Why would they trust us? When you look at it from the stranger’s perspective, there are many risks, but few advantages to just saying, “Hi.” This leads me to believe that the only contact likely to be made would be a preemptive strike.

Three things. First thing that came to mind about resource harvesting, gravity well and whatnot; “Planet Jackers”, as silly as it was (if you get the reference) with that sort of advanced technology it’s entirely feasible though I would probably upgrade the concept to solar system jackers. Really, why would they leave anything at all?

Two, yes to the interstellar freeway system. Earth could end up just another truck stop of the galaxy.

And lastly, that first page of comments on the Times page was nearly nothing but mouthy, ignorant, rubes. I mean they didn’t even give the idea a fighting chance before launching into “ah, this all a bunch of crap since science is anti-religious bull…” Seriously, is there some sort of ID, Luddite, flash-mob app out there?

Here’s the problem: probability is a function of two things. It’s a function of the size of the set — in this case billions upon billions of potential planets — but it’s also a function of the probability that each individual planet will develop life. And that is something we just don’t know.

Is it one in ten? Is it one in a million? Or is the probability of a given planet developing life more like one in infinity? That would make our own existence improbable, but it would also mean the odds of life elsewhere in the universe are literally zero.

This is grade 9 level maths; I would have expected a little more rigor from Stephen Hawking, even if he is just playing the part of enfant terrible.

My head just exploded. The existence of literally any conceivable event is now as likely as getting heads in a coin toss. Now THAT’S science.

PS @ millrick
“wow! you’re really calling Hawking on his math?
question: who was the Lucasian Professor of Mathematics at the University of Cambridge for thirty years? you or Hawking?”

The fact that Hawking — Lucasian Professor of Mathematics at the University of Cambridge for thirty years — is making a logical error so glaring is what astounds me.

Right now, in terms of knowing how likely life is to occur, we have a sample size of one. That’s not large enough to draw any conclusions from. We will probably never have a sample size large enough to draw conclusions of probability from. This isn’t science, it’s metaphysics. Which is fine — just call it metaphysics. Hawking expresses his *opinion*, but backs it up with what he calls “mathematics” and “rationality,” which is disingenuous — reason and math have nothing to say on the subject.

Granted, it’s only a theory, but what if they are here for our caca. One thing in limited quantities elsewhere, but abundant here, is human excrement. Kinda explains the recurring theme of anal probes, doesn’t it. Surveying for the resources they find precious. I humbly suggest that we stop trying to process our poop and start stockpiling it instead, just in case. Otherwise, they will be pretty pissed off at coming all this way, only to find us sequestering and rendering what they hold dear. I’d hate to see them start strip mining for the stuff. Wouldn’t be a pretty sight.

Much as I disagree with most of what Hawkins has to say, I think of him as a genius with a special vision that only someone who as studied something as he has would posses.

Hit point is simple and good.

The natural instinct is to fear a dark cave because of the unknown it could contain. Yet that instinct seems to get suspended, even displaced by wonder and speculation, because the Universe is to big to conceive, to big for that instinct to respond too.

Hawkins knows the Universe better than most will ever know anything.

Pragmatically speaking, we are alone in a cold, empty, fiery desert. Although a popular argument is that we are arrogant to consider ourselves the only life, it is also arrogant to think we could be sure of anything we can’t verify in such a wild and gargantuan Universe, including the possibility that we are a freak occurance.

However, if there is something capable of traveling here, it would have as little use for us as we would probably have for it. (The expectation that we could even learn from something so advanced is arrogant too. Star Trek–comparing space travel to some sort of hyped-up sea travel–a case in point of how foolishly we approach the issue.) It would be here for reasons of its own. We would not likely be on its conscious radar, despite our dreamy Star Trek ideas, and we should not encourage it until we are many more millennia advanced from here.

Hawking is too old for this stuff..
We humans are aliens of the worst kind. Can’t be worser than that.
Aliens that are advanced enough to travel here must be spiritually enlightened to be able to deal with us violent species.

Clearly, what we really need to do is focus on attacking and destroying Alien life, preemptively. We should be building massive planet destroying weapons.

After all, we’re the ones that wiped out all the indigenous people in America. Heck, if a hundred drunk Spaniards can wipe out the Aztecs, we should be able to kick some blue people’s asses. I say we get ready to expand our civilization by kicking it up to the next level.

“Waves of colonization have tended to be caused by miserable conditions among the colonizers and promise of wealth elsewhere. Technological advances tend to come from periods of warfare.”

I agreed at first, but after some thought…

Technological advances come from Science. Sadly, sometimes the public backing required is motivated by war (Manhattan project). Other times it is motivated by exploration (Velcro/NASA). People also tend to take peaceful tech in existence and weaponize it (Shovel in Zombie attack, Shoe in spider attack)

War and Colonization are basically about distribution of resources. “We don’t get enough stuff, lets go and take some of their stuff. If they resist, we’ll fight them”

Another option to grow your “stuff” is through efficiency/tech. This requires Science, which needs public backing. Business won’t build LHCs or Hubbles.

Science is our best bet if and when we have first contact, regardless of who initiates it.
Maybe they will see we are compassionate creatures that care for our own and others. That we possess a respect and natural wonder about the universe. That we mean them no harm and might enrich their lives/culture.
I fear that if we were put in contact today, either by our own or their efforts, we would be found sorely lacking. A dirty, wasteful and bellicose brood whose only concern is self. A danger to our species and those around us. A threat to be eliminated; if not for their own self-preservation, then that of all other life on earth.

In short, We need to get our $hit together before we start trying to contact others. Or pray to God that our smallpox can kick their smallpox’s ass.

“Maybe they will see we are compassionate creatures that care for our own and others. That we possess a respect and natural wonder about the universe. That we mean them no harm and might enrich their lives/culture.”

In short, maybe they’d happen to have a close version of a subset of the various human morality systems. Seems a bit of a long shot.

Of course, considering the differences in power between a starfaring civilization and ours, they might well do what we do when watching a tribe of apes– continue to let them do what they do without judging at all for good or for ill. Why assume that human values– _any_ human values– would have the slightest bit of significance to an alien?

it strikes me that not one comment here yet seems to take into account the sheer size (and age) of the universe — not only right now, but as it will be as the entire thing draws to a close.

let us suppose we as a species intend to last long enough to have our descendants be there at the quiet death of the universe, when the last bit of usable energy finally loses its potential, and the entire thing becomes one very cold mass of evenly distributed particles doing exactly nothing.

the species that has the privilege of seeing something anywhere near the end of this process we call the universe will need to learn some extraordinary sustainability practices: they’ll have to learn really really get their dollar’s worth out of every last bit of usable energy — as they frantically try and undertake the largest and most important civil engineering project in the history of the universe: the stopping and reversing of the big crunch.

any species that is not contributing to this effort will be seen as much too harmful to keep around.

THAT is the reason an alien species will wipe us out, if they get here before we get there.

“someone” will be the last species in the universe — and they’ll get that way be learning to conserve, and to kill any and every other thing that doesn’t aid in that process.

what are the odds that it will be homo sapiens descendants that end up in that position?

surely, it is near zero.

but it might not be exactly zero, so in the meantime, while we still have a chance to be THE species of intelligent life that makes the trip through the next 297,000 trillion billion billion years….

perhaps it might just do to keep our heads low and try NOT to be so conspicuous about wasting the precious resources of the universe: after all, it’s the only one we’ve got.

Hawking is a peerless mathematician and theoretical physicist, but he doesn’t have much of a track record on international relations or sociology. Not to mention interstellar relations and exosociology.

So as far as I can tell he’s just talking out his Hawking Hole. Of all people I expected him to not be a Shoot First, Ask Questions Later kinda guy.

Besides, its far too late for us to not alert the rest of the universe to our presence. Anyone within a hundred light years with a good telescope will be able to see us romping around down here.

So… Hawking made a documentary about how the Universe is like Central Park at night, except that there are no police officers, and the night never ends. He should have spoken up sooner, like before the We Are the World broadcast.

Just as a thought, many crickets live and make noise in Central Park. Most are completely ignored by the technologically superior mammals that wander in there, who are much more interested in one another.

But who is the Journal of Quantum Physics going to believe, him or us?

Lots of paranoia and misanthropy on display; are we all so ashamed of our family that we don’t want to bring home any new friends to meet them? And are we so lame that we’re scared to let anyone know where we live?

Also, why assume hiding is a good long-term strategy? Sooner or later, you will be found, and the gap in tech levels will just be worse the longer you delay contact. Perhaps initiating contact will earn respect; assuming we don’t get screwed over badly in the early stages, it should accelerate our social and technological evolution to the point that our civilization gets treated as an equal with other interplanetary powers.

I vote for genetic diversity. What if aliens wanted toenails? Or if toucan noses became fashionable? Life, the variety of life, the possible applications of life, the way life is put together—what makes earth unique would also make it valuable.

Hawking has an excellent point. You can be as warm and fuzzy and pure of heart as you wish, but the simple evolutionary science of self preservation means that we will meet a mixed bag of species (benevolent and rapacious, varying by individual and agency) just as we meet here on Earth.
Is there other intelligent life? Well, as my husband says “I’d hate to think we’re the best the Universe can do!”.
And are we vulnerable at this stage of our tech and development? You betcha.
Whenever I think on it, my dearest hope is that the abductee stories are true, and aliens ARE bagging/tagging/tracking human specimens just like we do with the bears in Yellowstone. That infers that there is a (fairly) benevolent/curious association of individuals studying us as a species. And if there are scientists/”Park rangers” studying us, there’s hope that our planet has been staked out as kind of an interstellar aboriginal preserve providing not perhaps perfect protection, but at least some buffer between our pre-interstellar civilization and the potential light-speed school yard bullies out there.

i guess what he meant to say is: whether or not they came to just say hi, chances are we do not survive it. ‘Can’t be those flimsy bioforms down there, doing all the thinking, wha’?’ – ‘Nah, pro’lly underground or something. Pump up the volume.’

Hawking is wrong because any alien civilization that has mastered interstellar travel (required for reaching Earth in the first place) would have also mastered unlimited energy (for example by somehow converting dark energy to visible energy) and unlimited resources (for example by using unlimited energy to manipulate matter at the nuclear level). Thus, such an advanced alien civilization would have no need for Earth’s resources or technology. Moreover, the energy required to haul Earth’s resources back to their world would be many times larger than the energy required to create those same resources from freely-available nuclear particles (for example by fusion or neutron bombardment). Moreover, such a civilization would have no desire to engage in interstellar travel because such travel would be pointless (except to flee a dying star, see below); the civilization simply would not have become so advanced if it were prone to engaging in pointless exercises. Finally, if an advanced alien civilization did have to flee a dying star, it would do so by creating a self-contained “floating world of consciousness” (something like the Matrix but without the physical part) that would drift through space for eternity (or at least the end of the universe) — yes, essentially “souls” in “heaven”. Such an ethereal floating world (actual size unknown) would want to avoid places like our solar system. Thus, it is probable that no two alien civilizations will ever meet in this universe unless their planets are close enough by coincidence so that the civilizations discover each other during experimental interstellar travel. In that unlikely circumstance, I suppose Hawkins could potentially be right.

It never fails to amuse me…these ponderings of what alien life might or might not do or be like. Head’s up folks. The key word here is ALIEN. As in totally and completely unlike us in any way shape or form.

I find it interesting that Hawking, as an American, sees the universe the way Americans seem to see most things – “it’s a threat, shoot at it!”. Maybe the aliens would be amazed to find that there really are other creatures out there, like finally bumping into someone, anyone, after you’ve been wandering around the desert for weeks. As for whether the aliens are there, I’d say they are, despite the self-confirming statistics invented above. If all life needs is a fairly stable environment which can support complex molecules like proteins, who’s to say it isn’t all over the place? Life we can relate to or even communicate with is probably rarer, granted but that’s an assumption, I have no evidence for it. It’s all beer talk until we find something out there, if we survive long enough to go and look.

Alien microbes might be _so_ alien that they pose no threat to us. Our bodies might not be the right environment for them for a number of reasons, temperature or chemical incompatability, for example.

The last intelligent species in the universe might not be worried with teasing out the last bit of energy and wiping out any rivals who aren’t fighting the fight against inevitable entropy. They might, instead, have a philosphy that lets them accept the end of the universe.

I’d say probably. Most of the time when we expose microbes to a completely unfamiliar chemical compound (polystyrene, nylon, etc.), it’s decades before any figure out how to eat it. To an alien microbe, you’d expect everything to be like that.

What about the possibility that life is fairly abundant, but that the time scales are so great that we never or rarely meet? Isn’t it plausible that intelligent civilizations develop, run their course for a few million years, and then burn out? Modern humans are, what, a couple of hundred thousand years old? Do we really expect to still be here on this rock in a million more? Why isn’t it quite possible that a relatively close civilization evolved, developed, lived and thrived for a few million years and then destroyed itself, ran out of resources, etc.? All their signals and data going through space in this direction passed us half a billion years ago, followed by silence. And here we are wondering where they are.

I think we’re not only looking through time and space for life, but for an even grossly similar level of development happening simultaneously with our own. On the other hand, maybe we’ll suddenly start getting 2 billion year old I Love Lucy re-runs from some other corner of the galaxy any day now.

This doesn’t even get into life forms that develop on much faster or slower time scales. This, to me, seems more likely than humanity and a few other players staying around until an end-of-universe Risk game.

He’s assuming that humans have any sort of control over this first contact thing. We can’t even control the thermostat of this house, never mind make it to the telephone!

He’s also assuming that if/when first contact is made, he’ll be one of the first to get the memo. There’s no reason to assume that aliens would want to talk to all of us at once. When we send scientists in to study savages, do we arm them with loudspeakers?

On the other hand, if aliens want to talk to all of us at once, then it’s a safe bet that their intentions are not to make us happy.

We have a lot more control over how our own primitive natives are treated, then how quickly we make contact with the larger neighborhood. It might be a good time to clean up our species’ resume a bit. Stop bullying the locals, and sterilize the probes we send to land on other planets. Just for starters…

In 1950 Enrico Fermi figured out that any civilization slightly more advanced than ours would be able to construct self-reproducing space probes and would soon (in Galactic time frame) be able to monitor all stars in its galaxy for anything of interest and carry out any desired missions anywhere and everywhere. See Fermi Paradox for more details.

I would apply Fermi’s argument to Hawking’s thusly:

A pre-singularity extraterrestrial intelligence is harmless to us.

A post-singularity extraterrestrial intelligence that wanted to find us and/or do anything with or to us would get its way.

Stephen Hawking appears to me to be way off on this one.
Any civilisation that has reached the stage of interstellar travel will;
1) Have long learned the value of peace, as interstellar travel will require co-operation and co-operation will require peace.
and
2) Have learned to exist quite happily on their travelling craft as it will require many many years to reach our planet from even the nearest star.
(We can discount light-speed travel as any object with mass requires INFINITE energy to propel it at such speeds).

I think he’s just sore because his theory of Hawking Radiation remains just that, and that was the one thing that was to be his legacy.

It doesnt really matter, what aliens are like and if they’re hostile, friendly, red or green or grey. The issue is more of a “systemic” nature: humanity is “hollywoodtized” to now lack the ability of having an open mind towards encouters with alien beings. Just imagine the polarization it would cause… some would hope for a extrinsic help to our homemade problems, some would start worshipping the visitors right away and others might happily join mass-suicides. From a humanity-point-of-view it would be best, if we never encountered other species, cause ours is already a mean piece of work. Not that humanity is bad or so – but just think of over 6 billion ppl being freaked out after that massive educational TV-BS like Godzilla and Independence Day etc – u name it.

I personally and scientifically second Hawing’s opinion: life’s out there. Do I want to meet “them” – sure, why not? Do I think humanity is mentally and otherwise fit to have unchallangable evidence of extraterrestial life – naw… just think on how the fuel-price would go nutz on us. E.T. – if you’re reading this (and I KNOW that you visit boingboing frequently with earthly pseudonyms): no hard feelings buddy. But stay the hell away from us – we could go postal on ourselves before you even set foot/tentacle on our planet. Oh – and thanks for Gillian Anderson and David Duchovny – you can have ’em back. PLEASE!

Tom Asbrook covered this really will in “On Point.” He and his guests loose the dreaminess that a real alien may or may not rip out of an idealist’s heart on contact. But he preserves the wonder of it all.

The notion that they would need a very good reason to come all the way from their home to our planet doesn’t account that:
– maybe the spaceship IS their home;
– maybe they’re going somewhere else and the opportunity to stop by presents itself;
– maybe they’re just curious to find other lifeforms. That might be a reward in itself, we don’t have to have anything else to offer. We hope to find microorganisms in our solar system, but we don’t expect to be able to talk to them after all.
– maybe they’re bored and there’s nowhere else to go.